Pressure sensitive adhesive bandages are used for application to various parts of the body to protect wounds from contamination, to reduce the danger of infection and to guard the wound against any further injury. These adhesive bandages usually comprise a backing, a cushion or pad, a facing, and a pressure sensitive adhesive mass coated on portions of one side of the backing. Each of these components performs a specific function in the pressure sensitive adhesive bandage and contributes to the suitability of the same for many purposes. The desirability of having adhesive bandages satisfy various objectives imposes many requirements and limitations on such bandages.
Studies have determined that during the varied daily activities of an individual, portions of the human skin normally stretch up to about 20 or 30 percent of its unstretched size and, at times, a skin stretching of about 50 percent may occur. In view of such findings, it has been determined that the ideal pressure sensitive adhesive bandage for use on the human body should have a low elastic modulus as well as high measure of elongation so that the adhesive bandage can conform to the movement of the underlying skin to which it is affixed. Thus, for example, when an adhesive bandage is applied to flexural joints such as fingers, elbows or knees, which are subjected to extensive stretching and, to a lesser degree, constriction and other distortion during normal activities, the bandage will easily stretch with the skin and substantially follow the changing contours of the skin. If the relative movement between the bandage and the skin is thus minimized, the wearer will be more comfortable and mechanical irritation will be substantially eliminated because tension on the skin will have been minimized. There will also be relatively little shifting of the adhesive bandage with respect to the skin, thereby lengthening the adhesive life of the adhesive bandage and reducing the objectionable transfer of the adhesive from the bandage to the skin. Furthermore, lengthening the adhesive life of the bandage will reduce the frequency of replacement of the bandages thereby allowing longer undisturbed healing times to the wound covered by such an adhesive bandage.
In addition to the desired elasticity and modulus properties, a desirable pressure sensitive adhesive bandage should also have a relatively high moisture vapor transmission rate in order that perspiration and other fluids on the surface of the skin may be transmitted through the bandage thereby resulting in reduced maceration of the underlying skin.
Sufficient tensile strength is another important requirement of pressure sensitive adhesive bandages in order that splitting or tearing does not occur when they are utilized. Sufficient tensile strength may not be provided merely by increasing the thickness of the bandage because thicker bandages have a tendency to roll off or peel, particularly adjacent to their edges. The problem of roll off or peel associated with such thick bandages is compounded by the surface friction of certain materials normally employed in the manufacture of adhesive bandages. For this reason, it is important that adhesive bandages be made of relatively thin materials with sufficient tensile strength to provide for the integrity of the bandage while still maintaining a low surface friction to minimize rub-off or abrasion by objects contacting the adhesive bandages in use, such as, for example, clothes.
It has been found that adhesive bandages utilizing conventional backing materials are deficient in one or more of the desired properties described above. For example, vinyl backings, such as plasticized polyvinyl chloride film or foam, have adequate strength and slip properties but lack the necessary modulus of elasticity to give good conformability to the bandages, especially when these bandages are applied to flexural joints, such as fingers, elbows or knee joints. On the other hand, polyurethane foams, which have been also suggested for use as adhesive bandage backings, provide good conformability, but have relatively high surface friction and low tensile strength. Styrene-butadiene rubber foams have also been tried as backing materials in the prior art without much success due to their insufficient strength. Natural rubber latex foams have excellent conformability characteristics and high strength, however, they present the disadvantage of having a high friction surface.
It is to these prior-art problems of limited elasticity and conformability and poor splitting and tear resistance, coupled with high surface friction, that the present invention is specifically directed, although the adhesive bandage backings of the present invention also excel in meeting the various other requirements for a high quality adhesive bandage, including the important requirement of "breathability."
It is therefore a general object of the present invention to provide a pressure sensitive adhesive bandage backing which meets the desired requirements for such a product. It is a more specific object to provide an adhesive bandage backing which is conformable to irregularly-shaped body portions and sufficiently thin to minimize peeling as a result of friction and contact with other objects. It is still another object to provide a pressure sensitive adhesive bandage backing which will conform to the various parts of the body regardless of the normal movement or change in shape thereof. These and other objects of the present invention will become more apparent from the description hereinafter.